If leaking on a slant, the leak source is coming from the high side. It could be traveling the entire distance of the rv. Use a level to see how the rv is leaning while parked where you discovered this.
30 feet from : My cabover roof had a leak on the passenger side. I discovered the water leaking out near my dump valve on the driver side rear . It traveled across the 8’ rv width then down the entire length. That water can and will mix with anything along the way while seeking a low point to escape. Sometimes the liquid will puddle enroute.
The water entered at the roof passenger side
Then rearward along the overhead Queen bed
It then ran down behind the passenger seat
It then ran across the floor to the drivers side, then along the drivers side, out the rear.
